Hey Folks,
I have recently picked up a Coronado AM/FM tube radio from a local antique store. The AM section works great but the FM section has extremely low output on only two channel it is able to tune into. I narrowed down the root cause to IF input and output transformers and possibly a ratio detector transformer having silver mica disease. I removed the transformers, checked for continuity, and removed the diseased internal mica wafers. I did the same for the AM IF cans and bridged each winding with a 100 pf cap.
Now, I am struggling to know what cap values I need for the FM IF and ratio detector transformers. I did a quick search on the web and it looks like the value is typically much less than 100 pf. To those that are knowledgeable in tube radios, could you shed some light on this for me? Measuring wafer mica capacitance is not an option for me as the wafers were destroyed during the removal process.
Thanks,
Min